1. Field of the Invention
The present invention relates generally to coal liquefaction product deashing processes and, more particularly but not by way of limitation to improved separation techniques in coal liquefaction product deashing processes.
2. Description of the Prior Art
Various coal liquefaction processes have been developed in the past wherein coal has been treated with one or more solvents and processed to separate the resulting insoluble coal products from the soluble coal products.
U.S. Pat. No. 3,607,716 and U.S. Pat. No. 3,607,717 issued to Roach and assigned to the same assignee as the present invention, disclose processes wherein coal is contacted with a solvent and the resulting mixture then is separated into a heavy phase containing the insoluble coal products and a light phase containing the soluble coal products. Other processes for separating the soluble coal products from the insoluble coal products present in coal liquefaction products utilizing one or more solvents are disclosed In U.S. Pat. Nos. 3,607,718 and 3,642,608, both issued to Roach et al., and assigned to the same assignee as the present invention.
While those processes provide a means for substantially separating the soluble coal products from the insoluble coal products, some soluble coal products still are separated with the insoluble materials in the heavy phase. It would be desirable to increase the mineral matter content of the insoluble coal products comprising the heavy phase to reduce the loss of valuable soluble coal products also contained therein.